diff --git a/src/Microsoft.Net.Http.Server/project.json b/src/Microsoft.Net.Http.Server/project.json
index 8d12e7b336..52e4499c32 100644
--- a/src/Microsoft.Net.Http.Server/project.json
+++ b/src/Microsoft.Net.Http.Server/project.json
@@ -15,7 +15,11 @@
     "xmlDoc": true
   },
   "frameworks": {
-    "net451": {},
+    "net451": {
+      "frameworkAssemblies": {
+        "System.Runtime": { "type": "build" }
+      }
+    },
     "netstandard1.3": {
       "dependencies": {
         "Microsoft.Win32.Primitives": "4.0.1-*",